The Fischer-Tropsch process is one of several processes involving the hydrogenation of carbon monoxide and is well-known for producing hydrocarbons and hydrocarbon fuels by contacting mixtures of carbon-monoxide/hydrogen, with generally an iron-based catalyst. The produced hydrocarbons usually contain a broad range of liquid paraffins and olefins of C.sub.5 -C.sub.20 carbon number, and under conditions of excess hydrogen, an especially valuable portion being the linear and branched paraffinic C.sub.6 -C.sub.11 fraction, the well-known "gasoline" fraction useful for internal combustion engines.
An extensive amount of work has been carried out in an effort to modify and improve the selectivity of the process in producing the gasoline fraction directly under efficient process conditions, having improved octane number. Particular process conditions which are highly desirable to achieve these goals are high percent CO conversion, low methane make, high liquid hydrocarbon make containing aromatics and olefins in the C.sub.5 -C.sub.11 hydrocarbon fraction and a low wax make (i.e., C.sub.23+ hydrocarbons).
A commercially practiced Fischer-Tropsch process uses mixtures of carbon monoxide/hydrogen that are contacted with a potassium-doped iron catalyst, as a fluid bed, at about 320.degree. C. to 330.degree. C. under pressure. However, a significant quantity of wax formation occurs, and further, the resulting liquid hydrocarbons generally only comprise about 5 weight percent aromatics.
What is desired in the art is a process which is more selective in producing C.sub.6 -C.sub.11 liquid hydrocarbons and in producing aromatics and olefins particularly in the C.sub.6 -C.sub.11 liquid hydrocarbon portion. Particularly desired is where the process can be conducted under very efficient conditions of high percent CO conversion, high liquid hydrocarbon make, containing C.sub.6 -C.sub.11 aromatics and/or alpha olefins, low methane make and low C.sub.23+ hydrocarbon wax make.